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To: PHP internals <internals@lists.php.net>
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Date: Wed, 6 Nov 2019 14:02:31 +0100
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Subject: file_cache is prone to some configuration changes
From: cmbecker69@gmx.de ("Christoph M. Becker")

Hi internals,

while having had a closer look at <https://bugs.php.net/78754>, I
learned that OPcache's file_cache is prone to some configuration
changes, which may cause PHP segfaults (and maybe other malfunctions).
For instance, if Xdebug is enabled while a file is compiled, but later
disabled when executing that file, the process is segfaulting because
the cached file relies on user opcode handlers which are no longer
available without Xdebug loaded.  I'm presenting Xdebug as example
because that likely caused the issues reported in that ticket, but
basically any extension can call zend_set_user_opcode_handler() to
install user opcode handlers, causing the same problems.

It should be mentioned that, to my knowledge, shared memory caches are
not affected by this (except for Windows), because re-attaching a
differently configured php instance isn't possible at all.

Anyhow, should we fix this (assuming a general fix would be possible),
or would that be rather a documentation issue, based on the assumption
that such configuration changes don't make sense in combination with
OPcache at all (IOW, if such changes are done, users should reset OPcache)=
.

=2D-
Christoph M. Becker